Indexing motion packaging machines are used for producing double webbed packages used in a variety of applications, such as for packaging systems of food products like frankfurters, luncheon meats, cheese or the like. In such packaging systems, a bottom forming web is fitted into the packaging machine at a tail end of the machine and supported from an arbor system such as described in copending U.S. patent application Ser. No. 08/531,071 filed Sep. 20, 1995 in the name of the inventor of this application. The bottom forming web is fed via a dancer arm arrangement to a gripper chain which advances the forming web to a vacuum forming box system which vacuum forms the bottom web in an upwardly facing cavity within which the product is loaded. The formed web and product are then advanced downstream where a second or top web is fed in and sealed to the formed web over the product and product cavity. The double webbed, sealed package is then discharged from the machine, and longitudinal and transverse cuts are made to separate the web and product into individual packages.
In order to provide the sealed packages with information such as logos, trademarks, cooking instructions, nutritional information, etc., it is necessary to provide the bottom forming web with the noted information pre-printed thereon at regular intervals defined by small registration marks also pre-printed on the bottom web. The web printing is continually carried out so as to be slightly compressed and shorter than the known desired final spacing, due to inaccuracies in the printing process and variables in the web film being printed so that the end user must stretch the film as desired to obtain the final spacing. Further, the information on the web is distorted such that it appears normal after the web has been formed to define the product-receiving cavity.
Some prior art systems have attempted to attain the correct registration of the pre-printed web by heating the entirety of the web to provide a certain amount of stretch as the web is fed into the packaging machine. However, such systems have proven difficult to control in that the web film loses its rigidity and is difficult to advance through the machine.
There remains a need, especially in the packaging field, to provide a registration control system for consistently stretching and heating a pre-printed web to obtain accurate and precise intervals in which distorted printing is effectively transformed into legible information consistently and properly positioned on each package.
It is one object of the present invention to provide a registration control system for the bottom forming web of an indexing motion packaging machine. It is another object of the present invention to provide a web registration control system utilizing a braking arrangement, a photosensing mechanism and a heater system for enabling the transformation of distorted information pre-printed on the web. It is another object of the present invention to provide a web registration control system which relies on a combination of stretching and heating applied to the web between a supply roll and a web advancement mechanism. It is a further object of the present invention to provide a web registration control system which offers repeatability and consistency in correctly positioning a forming web. Yet another object of the present invention is a method of obtaining precise registration of a forming web in an indexing motion packaging machine. Still yet another object of the present invention is to provide a web registration control system which is easily accommodated between a web supply roll and a web advancement mechanism.
In one aspect of the invention, there is provided a registration control system for a movable web pre-printed with a series of registration marks and fed from a supply roll by an unwind motor. The system includes a framework on which the supply roll and the unwind motor are mounted. A braking arrangement is connected to the framework and is selectively engaged with the web to stop the unwinding thereof. A photosensing mechanism is located downstream from the braking arrangement on the framework for sensing a registration mark on the web. A heater system is disposed downstream from the photosensing mechanism on the framework for selectively applying heat to the web upon the next registration mark downstream from the registration mark sensed at the photosensing mechanism. The web is engageable with a nip roller arrangement formed by a pair of spaced driven rollers disposed on the framework in driving engagement with the unwind motor and a nip roller located between the driven rollers and engaged with each driven roller. The braking arrangement includes a lower idler roller mounted on the framework, a brake roller movably connected on the framework, the web passing over the lower idler roller and the brake roller, and an actuating device for selectively moving the brake roller against the web and the lower idler roller. In the preferred embodiment, the actuating device is a first hydraulic cylinder having a cylinder end connected to the framework and a rod end joined to the brake roller. The photosensing mechanism is adjustably positioned on the framework relative to the braking arrangement. The photosensing mechanism includes a pair of opposed, elongated, substantially parallel guide channels, one on either side of the web, with one of the channels carrying a transmitting element and the other of the channels bearing a cooperating receiving element. The heater system is adjustably positioned on the framework relative to the photosensing mechanism. The heater system includes a pair of opposed heater elements between which the web is passed. One of the heater elements is selectively movable towards and away from the web and the other of the heater elements. One of the heater elements is associated with a rod end of a second hydraulic cylinder. An upper idler roller is disposed on the framework between the driven rollers and the heater system for engagement with the web.
Another aspect of the present invention relates to a web advancement mechanism having a selectively movable web fed from a supply roll by an unwind motor. The web has spaced registration marks for defining areas of distorted printing provided thereon. The improvement resides in a web registration control system located between the supply roll and the web advancement mechanism constructed and arranged to sense a registration mark on the web at a first location between the supply roll and the unwind motor, heat the web upon the next adjacent downstream registration mark while the web is stopped, and operate the unwind motor while the web is prevented from unwinding from the supply roll to create tension in a second location downstream of the first location. These functions are performed in a manner such that the web will be sufficiently stretched to a constant length to effectively transform the distorted printing into legible printing as the web continues being delivered into the web advancement mechanism which is preferably located in the indexing motion packaging machine. The web is engageable with a nip roller engagement located downstream from the second location, and formed by a pair of spaced driven rollers in driving engagement with the unwind motor and a nip roller located between the driven rollers and engaged with each driven roller. A dancer mechanism is located downstream of the nip roller arrangement for advancing the constant length of stretched web into the web advancement mechanism. The registration mark sensed on the web is detected by an adjustable photosensing mechanism. The web is prevented from unwinding from the supply roller by a braking arrangement located upstream of the photosensing mechanism and selectively engaged with the web upon detection of the registration mark by the photosensing mechanism. The web is heated in a localized area by a heater system disposed downstream from the photosensing mechanism.
Yet a further aspect of the invention relates to a method of registering a web fed from a supply roll by an unwind motor in a web advancement mechanism, the web having spaced registration marks for defining areas of distorted printing provided thereon. The method comprises the steps of: a) using the unwind motor to apply a stretching to the web upon sensing of a registration mark on the web fed from the supply roll and simultaneously stopping the web at a position upstream from the sensed registration mark; and b) heating the web upon the registration mark at a location spaced a predetermined distance downstream of the sensed mark. The combination of the stretching and heating transforms each area of distorted printing into legible printing as the web continues into the web advancement mechanism.
Still yet a further aspect of the invention relates to a method of obtaining precise registration of a forming web in an indexing motion web mechanism. The web has spaced registration marks for defining an area of distorted printing provided thereon. The method comprises the steps of: a) passing the web from a supply roll through a braking arrangement, a photosensing mechanism for sensing the registration marks on the web and a heater system movable back and forth relative to the web to a nip roller arrangement having one or more rolls driven by the unwind motor; b) indexing the web from the supply roll by operation of the unwind motor; c) sensing the presence of a first registration mark on the web by the photosensing mechanism; d) immediately stopping the feeding of the web from the supply roll using the braking arrangement; e) stretching the web downstream of the braking arrangement by continuing to operate the unwind motor to apply tension to the web; f) stopping the unwind motor; and g) applying heat to the web by moving the heater system towards the web upon the adjacent registration mark downstream of the first registration mark to attain a predetermined precise length for supply into the web advancement mechanism downstream of the nip roller arrangement.